Washington, Aug 29 (): Skywatchers can watch a so called “Blue Moon” on Friday Aug 31,2012. The next Blue Moon will appear only after three years.
The moon will not actually be blue in colour. But that is what some call the second full moon to occur within a month. Although the full moon on Friday night is not likely to be blue, it has been known to happen.
Usually months have only one full Moon, but occasionally a second one sneaks in. The first full Moon of this month occurred on August 1st in the Americas and on August 2nd in Europe, Africa, Asia, and Australia. Another full moon will rise second time on this month on August 31, which has come to be called as “Blue Moon.” However, it’s not at all clear where the term ‘Blue Moon’ comes from.
The moon takes about 29 and half days to go around the earth, and get back to the same point. QUT astrophysicist, Dr Stephen Hughes said, “Blue Moons occur only about seven times in 19 years—that’s about once every two-and-a-half years.”
A blue moon happens as a calendar catch-up because it takes the moon about 29 and a half days to go round the earth and since this is less than the number of days in a calendar month, two full moons can sometimes occur in a single month.
Full Moons are separated by 29 and half days. As most months are 30 or 31 days long, it is possible to fit two full moons in a single month.
Before 1946, a Blue Moon meant something else. For example, said Canadian folklorist Hiscock, sometimes it is referred to an obvious absurdity. There are reports of blue moons after the Krakatoa eruption in Indonesia in 1883 in which volcanic ash was ejected 80km high, on the edge of the ionosphere.
February is the only month that can never have a Blue Moon by this definition.